1. Threats to biological diversity 2: Over exploitation
Sam Hopkins
Biodiversity and Conservation Biology

2. What is Overexploitation?
Overexploitation is the use, by humans, of a natural resource to an extent that it is not sustainable
Overexploitation is the use in a non-sustainable way of a natural resources. (Images from

3. What causes overexploitation? 1
A number of factors contribute to overexploitation
Possibly the rich countries over consuming
Lack of incentives to conserve such as environmental taxes
Economic growth causes environmental degradation however lowering economic growth in the rich countries will in turn lower it in the poor countries
Increases in the human population number
There are many factor involved in overexploitation. Many blame the rich countries for over consuming but it is the poorer countries that are putting pressure on the natural world with a rapidly growing population. The estimations show that Africa will be at a population of 3 billion by the end of this century which is five times what it is now. This human pressure will displace the habitat of other species in the form of land for agriculture, urbanisation and infrastructure.. There is a lack of incentives for any country to clean up its act, if there were environmental taxes enforced worldwide then countries would by forced to take notice. It is suggested that economic growth causes environmental degradation but lowering the rich countries economic growth will in turn lower the poorer countries. As has already been mentioned the pressure put on the environment will carry on increasing as long as the human population carries on increasing, current estimates expect the human population to be around 12 billion by 2100 and all of these people will need a place to live, food to eat and clean water to drink.

4. Examples of overexploitation: The Aurochs 2
Was a member of the Bovidae family
Ranged from Britain to Africa
By the 13th century it was only seen in Poland, Lithuania and Prussia
By 1564 only 38 animals remained
Ban imposed over hunting
Hunted to extinction by 1627
The Aurochs is an example of overexploitation, showing that it is not a modern phenomenon. It was a member of the Bovidae family with a huge range from Britain all the way to Africa. By the 13th century it was only seen in Poland, Lithuania and Prussia and by 1564 it had been hunted down to 38 animals. At this point the rulers of the land imposed a ban on hunting the Aurochs that was punishable by death, they had noticed its rarity, but it only stopped the common folk from hunting it and by 1627 it was extinct. (Image from en.wikipedia.org/wiki/Aurochs)

5. Examples of overexploitation: The Sea Cow 3
The ship the St Peter became shipwrecked off Kamchutka in November 1741
They managed to survive by hunting the Sea Cow
The sea cow was estimated to be 28 feet long and 7-8 tons
When the shipwrecked men got off the island in Aug 1742 they told everyone about the sea cow when they got back
It had been hunted to extinction by 1768
The sea cow was a relation to the dugong or manatee. It was discovered by a group of sailors who had become shipwrecked off Kamchutka in November They survived on the Sea cow and reported that the sea cows were about 28 feet long and 7-8 tons and moved in the water in herds. When the shipwrecked men made their escape in the august of 1742 they told everyone back home about the riches to be had by hunting this sea cow and by 1768 the animal was extinct. (Image from explorenorth.com/library/yafeatures/bl_seacow)

6. Examples of overexploitation: The Great Auk 4
The Great Auk was a flightless sea bird
It was found in Canada, Greenland, Iceland, Norway, Ireland and Great Britain
As the animal had few natural predators it had no fear of humans which made them easier to hunt
Great Auk was hunted for food and feathers used for stuffing mattresses
The last pair were killed while sitting on an egg and for good measure the egg was smashed
The great Auk is another example of our ancestors being particularly ignorant. It was a flightless sea bird with a huge range in the North Atlantic. The bird had few natural predators and so was unafraid of humans and with it being flightless it was a hunters dream. The bird was used for food and feathers and when it became rare it was quite the thing to have one stuffed or keep its eggs. The last pair were killed by a particularly evil hunter who not only killed both the adults but also smashed the egg for good measure. (Image from en.wikipedia.org/wiki/Great_Auk)

7. Examples of overexploitation: The Passenger Pigeon 5
The passenger pigeon was a flocking bird found in North America
Estimates suggest that there were at least 3 billion individuals
The birds roosted together which made them an easy target
The hunter came up with several ingenious ways of killing the birds; suffocation by burning grass, fed alcohol soaked grain, beaten down with long sticks, netted and trapped using a decoy
The last one was seen in 1900 in Ohio
The last example I have for you of humans ignorance is the demise of the passenger pigeon. This bird was seen in huge numbers in North America and was an easy target as they all roosted together. The hunters thought up many cruel ways to kill these birds ranging from feeding them grain soaked in alcohol to beating them down with long sticks. By 1900 all of the birds had gone. (Image from

8. Examples of overexploitation: The fur trade
The whole of the fur trade is an example of overexploitation
In the past when one animal has become rare the trade has just looked for another source to keep people in fashion
At the height of the squirrel trade half a million skins were exported each year
As land stocks of squirrels and minks became depleted the sea was looked to
This lead to the demise of the sea otter and by 1911 there were only left
The whole fur trade is an example of overexploitation. Animals are killed for their pelts for human vanity and no more. When one species with suitable fur becomes scarce then an alternative is looked for, this has lead the trade to go from squirrels to minks to sea otters and has left depleted animal numbers wherever it looks. (Images from peterpalms.com)

9. The fishing industry
One of the most well known examples of over exploitation is by the fishing industry
Commercial fishing fleets exceed the ecological limit
This has been caused by greed, a lack of data on actual fish stocks and better fishing equipment6
Out of the known 21,000 fish species only 9,000 are actually used by humans7
22 species are harvested in excess of 100,000 tonnes per year7
In the great lakes in North America there has been a decline in fish numbers and the lake trout and Atlantic Salmon are extinct in Lake Ontario8
A good example of over exploitation is seen in the fishing industry. There are 21,000 fish species known to science and only 9,000 of these are utilised. Only 22 of these species are harvested in excess of 100,000 tonnes per year. Fish stocks are declining across the globe in salt and fresh water. In the great lakes in north America there has been an over all decline in fish numbers due to over fishing and 2 species have gone extinct in one of the lakes. (Image from akiskayehtcharters.com)

10. The fishing industry 8
The numbers of fish taken every year has declined recently but on average
500,000 tons of fish are taken from the Mekong river in S.E. Asia
210,000 tons of fish are taken from the Zaire river in Africa
210,000 tons of fish are taken from the Amazon river in S. America
Now fishermen are fishing down the food chain, as they cannot get the top predatory fish anymore they go for pelagic fish
Here are some figures on the amount of fish taken from 3 rivers throughout the world. Fish seem to be considered an endless resource by some people. Now fishermen are fishing down the food chain because they have exhausted the supply of predatory fish they are now looking to the pelagic fish to keep their profits up. For an overview of over fishing look at (Images from url.co.nz,

11. The Amphibian and Reptile Industry 9
The exploitation of Reptiles and Amphibians can be traced back to the Romans
In a book called Natural History Pliny wrote
“Romans carried stones from a crocodiles belly as charms against aching joints, bound crocodile teeth to their arms as an aphrodisiac, treated whooping cough in their children with doses of crocodile meet, and trustfully administered burned crocodile skin mixed with vinegar as an aesthetic to patients about to undergo surgery. Woman used crocodile dung in a lint tampon as a contraceptive”
It wasn’t just the Romans however, the Ancient people of America used toad secretions as a hallucinogen during religious ceremonies
As a case study I want to look at the exploitation of herptiles by humans. This exploitation has gone on for centuries. Pliny wrote a book entitled ‘Natural History’ and in it is an account of the many uses of crocodiles. The ancient civilisations in America used toad secretions as a hallucinogen during religious ceremonies. Some of the artefacts that come from the sites of these ancient people are toad shape or have pictures of toads on them. (Image from

12. The Amphibian and Reptile Industry: Food 9
Amphibians and reptiles have long been used as a source of protein
Now they are served as a delicacy or oddity for example, frogs legs au gratin, frogs legs teriyaki
Amphibians and reptiles have always been used by humans as food, they are a good source of protein. Now they are more regarded as a delicacy or oddity rather than the staple of a few. (Images from crawfishcoofcentralflanc.com, gardkartsen.com, planetbarbecue.co.uk)

13. The Amphibian and Reptile Industry: Food 9
The commonly eaten frogs are Rana catesbeiana, Rana esculenta, Rana tigrina and Pyxicephalus adspersus
The commonly eaten reptiles are Green and Spiny Iguanas, Turtles, Crocodiles and Alligators
. Certain frog species are particularly persecuted along with a few lizards, turtles, crocodiles and alligators.(Images from norman.walsh.name,

14. The Amphibian and Reptile Industry: Food 9
Some facts and figures for you
The USA imported 2.5 million kilograms of frogs legs from Japan and India in 1976
Between 1979 and ,000kgs of alligator were sold every year
In the 1960s 150,000 Iguanas were eaten per year in Nicaragua alone
12 million fresh water turtles are sold to china from S.E. Asia per year
I have taken some figure from the literature for you so that you can see the enormity of this trade.

15. The Amphibian and Reptile Industry: Skins 9
Reptiles and Amphibians are also used for their skins
Reptiles skins make
Shoes
Purses
Belts
Amphibian skins make
Book binding
Glue
Fishing lures
The skins of these animals are also sought after, reptile skins are made into shoes, purses, belts etc and amphibian skins are also made into shoes purses and belts along with book bindings, glue and fishing lures. (Images from eastofedenleathers.com,designerleathercraft.co.uk,

16. The Amphibian and Reptile Industry: Skins 9
Some facts and figures for you
In 1981 alone 304,189 pairs of shoes were made from Boa constrictors and 176,204 from Python reticularis
Between 1980 and 1985 over 1 million Caiman crocodile skins were sold every year
12 million Tegu skins were imported between the years of
1-2 million Monitor skins are exported from Africa and Asia each year
In 1986, 10.5 million reptile skins were sold legally in the USA
Here are some figures to show you how large this trade is on top of the food industry. Notice that most of these are different species so they are additional to the food figures. All of these numbers are taken from legal trade, with the addition of illegal trade no one knows what the real numbers are.

17. The Amphibian and Reptile Industry: Cheap Souvenirs 9
One of the saddest trades is in cheap souvenirs
Around the world amphibians and reptiles are killed to make
Crocodile teeth necklaces
Crocodile feet key rings
Rattlesnake rattle key rings
Rattlesnake head/fang mementoes
Stuffed and varnished toads in amusing positions!
At least 115,000 horned lizards are thought to have been stuffed over the last 45 years
One of the most worthless use of a species is for cheap souvenirs. Unfortunately many of these animals end up as just that. Crocodiles have their feet and teeth taken, rattle snakes have their rattle taken and even frogs get stuffed and varnished to be used as ornaments. In the last 45 years it is estimated that 115,000 horned lizards were stuffed for souvenirs. (Images from

18. The Amphibian and Reptile Industry: Medicine (Traditional and Modern) 9
The use of amphibians and reptiles for medicinal purposes has gone on for centuries as the excerpt from the book ‘Natural History’ showed
Iranians use a broth made from snakes and tortoises to fight disease
Asians use fat from monitor lizards for bacterial infection
People in Pakistan use oil from monitor lizards as an aphrodisiac
In Madagascar the fat and oil from a crocodile will treat burns, ulcers and cancer
In the Dominican Republic and Haiti the fat from a crocodile cures asthma
An alkaloid from the Epipedobates frog is a pain killer more powerful than morphine
Using various parts of amphibians and reptiles as medicine goes back years as Pliny tells us. Here are some uses of animals and what they are supposed to cure. Snake and tortoise broth fights disease, fat from monitor lizards fights bacterial infection, oil from monitor lizards is an aphrodisiac, the fat and oil from a crocodile will treat burns, ulcers and cancer in Madagascar and will cure asthma in the Dominican Republic and Haiti. Scientists have found a frog that produces an alkaloid that in humans is a pain killer more powerful than morphine.

19. The Amphibian and Reptile Industry: Pet Trade 9
The exotic pet trade is growing rapidly
In 1990 the Florida Game and Freshwater fish commission noted the number of legal removals from the wild in Florida alone
In total 119,831 animals removed
49,240 snakes
41,493 frogs
1,050 salamanders
This is an under estimate as it only shows the traders that declared what they were taking
Between 1992 and ,000 Gulf Coast box turtles were taken from the wild
The pet trade is another drain on the amphibians and reptiles of the world. I have put in some figures of what people declared they were taking out of the wild in Florida but it is an underestimate because not everything will have been declared. Sadly most of these animals will die in transit or in bad conditions once they have been bought. Very few make it to an owner who knows what to do with it.

20. The Amphibian and Reptile Industry: Science, Research and Teaching 9
Amphibians and reptiles are taken from the wild as teaching aids in schools and universities
Used in dissections in schools and universities
In the 1970s it was estimated that 15 million leopard frogs were taken from the wild for dissection teaching
Now people are more aware and more specimens are grown in captivity for use in research and teaching
On top of everything else scientists are not helping the matter. Animals are taken from the wild in huge numbers for dissections. The leopard frog in the USA was collected in its millions for teaching although hopefully this is changing as more and more animals are being bred in the lab. However there is still collecting and shipping going on the South Africa of Xenopus laevis. (Image from

21. The Amphibian and Reptile Industry: The problems 9
As you can see from the enormous figures I have given you over the past few slides this industry is not sustainable
Many of these animals have very long lives and are slow to reach maturity and reproductive rates are low
Over exploitation is not their only problem, add to the fact habitat degradation, invasive species, peoples persecution etc. and there will be a problem
The reptiles and amphibians of the world cannot go on being utilised like this, the figures I have given you over the past few slides are enormous and most of these species have long lives, are slow to reach sexual maturity and have low reproductive rate. Add to this the problems with habitat destruction and invasive species and there is a very large problem. On top of all this is human persecution of amphibians and reptiles, the photograph here is taken from a ‘rattlesnake roundup’ in North America where thousands of Rattlesnakes are collected from the wild and there are events like timed snake skinning and here the two boys have paid $10 each to skin their own snake. (Image from

22. Overexploitation in Africa 10
This is not just a western problem, overexploitation is occurring in Africa too
In the 1970s in West Africa a form of Semi nomadic farming was practised
This was suitable for the habitat
Stocking rate was close to carrying capacity
After 15 years of drought this system was not working anymore and instead of giving money to the farmers to carry on, the government gave money for well digging and animal health care
The human population in the area has grown by 2-2.5% and to keep enough animals to feed everyone the system is being overexploited
Farmers are turning to sedentary farming either settling with their few remaining livestock or growing crops or they move to an urban area
The problem of overexploitation is not confined to the west, it is occurring in Africa as well. In west Africa there is a tradition of semi nomadic farming where the animals were taken to the north in the rainy season for good fodder and in the dry season permanent water was found. The stocking rate was close to the carrying capacity as it was set by the resources available. The system broke down after a 15 year period of drought where the government did nothing to help he farmers other than build wells and give money for animal health. This problem was exacerbated by the population growing at a rate of 2-2.5% per year. Trying to make enough food to feed everyone caused the system to become overexploited. Now farmers that were semi nomadic are becoming sedentary either with their remaining live stock or starting crop farming. The alternative that a lot of them have chosen is to move into towns and cities and look for work.

23. References
Fielder and Kaeiva (1998) Conservation Biology for the coming decade. Pp 396.
Wikipedia contributors, Aurochs [accessed 2006 July 10] Wikipedia, The free Encyclopaedia, 9th July 2006, 9:50 UTC, Available from: En.wikipedia.org/wiki/Aurochs
Lundberg, M. The Steller’s sea cow [cited date 2006 Jul 15]. Available from:
Wikipedia contributors, Great Auk, [accessed 2006 July 10] Wikipedia, The free Encyclopedia, Available from:En.wikipedia.org/wiki/Great_Auk
Smithsonian institute [cited date 2006 Jul 15] Available from:
US Environmental Protection Agency [cited date 2006 Jul 15]. Available from:
Fielder and Jain (1992) Conservation- the theory and practice of nature conservation, preservation and management. Pp 157
Cox, G.W. (1997) Conservation Biology concepts and applications. Pp 158.
Pough et al. (2001) Herpetology 2nd Ed. Pp 500
Breman, H. (1992) Desertification control, the West African case; prevention is better than cure. Biotropica 24: